Electronic fuel injection systems have injector valves with inductive coils for opening and closing the valves in timed relation. This timed relation requires rapid current buildup in the coils to accurately time the opening of the injector valves. Reduced current can then be applied to the coils to keep the valves open for a specified length of time, with the valves being closed at a precise time by cutting off the current in the coils. The magnetic characteristics of inductive coils, whether used in fuel injection systems for driving a magnetic valve, or in a mechanical relay, or even in certain magnetic memories, are such that once the magnetic field has been established by the buildup of current, maintenance of the field requires much less current, with the current needed varying in the range from one-half to one-tenth the amount needed to originally energize the field. This is because the energy necessary to pull in a valve or armature is greater than that required to hold the same operated.
Separate voltage and current regulators have been utilized in the past to energize coils, but no successful system has been designed which can automatically crossover from voltage regulation to precise current regulation, as is desired. In order to conserve space, it is desirable to have a regulator system of the aforementioned characteristics which can be incorporated into an integrated circuit chip.